The North Carolina Breast Cancer Screening Program (NC-BCSP) has conducted a ten-year effectiveness trial of a natural helper lay health advisor intervention in 10 counties (5 interventions, 5 comparisons) in eastern North Carolina to increase mammography use by low-income, rural, African American women. Three waves (baseline and 2 follow-ups) of interview data collected from a stratified random sample of, initially, 1000 Black women (500 intervention, 500 comparison) indicate that NC-BCSP's lay health advisor intervention was modestly effective overall after 30 months (at first follow-up IT2] in 1997), and associated with a greater increase in recent mammography use among specific subgroups, particularly women with annual family incomes under $12,000. The proposed exploratory study uses all three waves of cohort data to determine: 1) whether NC-BCSP's intervention effect was sustained over the full 8 years of the evaluation (T1-T3), and for which subgroups; 2) what factors are associated with, and what pathways mediated, the intervention's effect initially (T1 - T2,) and in the second follow-up period (T2-T3); 3) how successfully an existing administrative data set (Medicare) can be used, instead of self-report data, to evaluate intervention effectiveness; and 4) whether geographical proximity, as measured by GIS software, of lay advisors to cohort respondents can serve as a useful proxy for self-report measures of exposure to the lay advisors. Analyses will use multivariate models with logistic regression and generalized estimating equations to account for repeated mammography reports. The proposed secondary analyses of this unique longitudinal data set will provide valuable insights for designing more effective, better targeted, and more cost-effective interventions to reach the hardest-to-reach rural women still not being screened regularly. The goal of this grant is to understand the differences between continuous users, backsliders, late adopters and non-users of screening mammography, and the mechanisms, which explain variation in these groups' exposure to the intervention and their use, or non-use, of mammography.